講演者 : Melanie Koehler
(Institute of Planetology, Muenster University, Germany)
タイトル: Dust in the solar system and extra-solar planetary systems:
model calculations and laboratory measurements to study
optical properties
日時 : 2006年11月30日（木）16:00-17:30
場所 : 自然科学3号館6階セミナー室 609号室
Dust particles are observed in the solar system and in extra-solar planetary systems. Studying their properties and their spatial distribution helps to understand the evolution of those planetary systems. The optical properties of dust particles are not only important for interpretation of astronomical observations, but also, due to the radiation pressure force have some influence on the dust dynamics. In this presentation I will discuss results of numerical simulations, as well as laboratory measurements related to the optical properties of dust. Dust particles are usually irregularly shaped and are often assumed to have an aggregate structure. In this case radiation pressure force differs from that for compact spherical grains often used for model calculations. We have simulated the light scattering of aggregates consisting of spherical monomers to determine the variation of the optical properties with material composition and structure of the aggregates. These model calculations are so far only possibly for small particles, but we extrapolate the results to obtain an estimate for the radiation pressure force acting on dust particles in cometary trails and meteoroid streams. Especially the infrared thermal emission of the dust shows spectral features that are characteristic for the composition of dust. Laboratory measurements of the infrared spectra were taken from samples of primitive meteorites in the wavelength range 8 μm to 13 μ m. Spectra of Olivine as well as Pyroxene differ with changing iron-to-magnesium content and increasing temperature. We apply the obtained laboratory spectra to interpretations of the spectra of dust particles around young and main-sequence stars, comets and the Zodiacal light. |